#  highpass v 0.1 - A highpass filter.
#  Copyright (C) 2010 John Donovan - mersey.viking@gmail.com

#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at

#  http://www.apache.org/licenses/LICENSE-2.0

#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

import scipy.ndimage
import numpy.fft

def highpass(image, sigma):
    f = numpy.fft.rfft2(image)
    g = scipy.ndimage.fourier_gaussian(f, sigma, n=image.shape[1])
    h = numpy.fft.irfft2(g)
    return Image(h)
